According to Gizmodo UK, which used a freedom of information request to obtain details about TfL's mobile tracking experiment, use of the passenger data could help inform advertising decisions throughout the Tube network.
Although still a pilot project at this stage, TfL's four-week trial, which took place between mid-November and mid-December 2016, uncovered a mass of information that could help the organisation to improve the customer experience.
The trial, involving 54 out of the Underground's 270 stations, collected data from passengers whose mobile device or laptop had its wi-fi switched on.
Using the various wi-fi hotspots located around the Tube network, TfL identified users' unique media access control (MAC) address to collect wi-fi data at each participating station, and passengers were informed in advance that the trial would not identify individuals or monitor their browsing activity.
Among the findings, TfL was able to use the data to track the journeys that people actually took around the network and it said this evidence base would help to inform its planning decisions.
The trial also revealed that it is even possible to track a passenger's location within an individual station, which TfL suggested could enable it to provide real-time crowding information to its customers. The crowding data could also inform its decisions about how many staff would be needed at each station.
Such logistical improvements offer obvious benefits to passengers, but the study went on to examine whether the collection of data could boost advertising revenues at a time when the Underground is coming under increasing financial pressure.
As explained by Gizmodo UK: "According to a detailed grid outlining the rationale for the trial, the advertising upshot could be valued at hundreds of millions of pounds because TfL will be able to offer better analytics to advertisers about exactly how many people are looking at their ads around the tube network, because they know where you're standing."
Furthermore, being able to estimate the footfall in different parts of each station, and even roughly how long a Tube user stares at an ad, means TfL could offer differential pricing depending on how good each advertising slot is.
In other words, "as TfL know your commute, if you’re the consumer a company wants to attract, they'll know exactly the right places to buy ads so that you'll see them".
A recent Warc report, Crowds, products and places: how mobile is reinventing market research, explored how smartphones are providing brands with a wealth of location data.
Reporting from the MRMW Europe 2016 (Market Research in the Mobile World) event, it was revealed that Telefonica is currently working with Exterion, the OOH media owner, to use such data to help with media allocation at digital sites at inner London Tube stations.
Data sourced from Gizmodo UK; additional data by Warc staff